There is a very large installed base of solenoid-type electromechanical locks. Solenoid-type locks use a solenoid as the lock drive to move a locking element within the lock between a locked position and an unlocked position. In the locked position, the locking element is moved into interfering engagement with a lock component to prevent refraction of the latchbolt. In the unlocked position, the locking element is moved to a position that allows the latchbolt to be freely retracted.
The solenoid in a solenoid-type lock drive is typically powered by a solenoid lock control system having one of two operating voltages, 12 or 24 volts, which are standard in the industry. The solenoid lock control system may be a local control system mounted on or near the door to send power to its associated lock, or it may be a centralized system operating multiple doors independently or in concert to lock or unlock doors on a timed schedule, responsive to emergency conditions or for other reasons.
The solenoid of a solenoid-type lock drive is spring biased to a default state, which may be either the locked or unlocked state, depending on the intended application of the lock. When power is applied to the lock by the solenoid-type control system, the solenoid moves away from its default locked or unlocked state against the biasing spring force. As long as power is applied to the lock drive in the lock, the solenoid drive remains in its non-default state. As soon as power is removed by the control system the lock returns to its default state.
This feature of a solenoid-type lock drive—in which a spring in the lock automatically returns the lock to its default state—is relied upon in emergency conditions to ensure that the locks are all in a known locked or unlocked state when all power is removed. When the solenoid is spring biased to the locked position, the lock is referred to as a “fail secure” lock. When it is spring biased to the unlocked position the lock is referred to as a “fail safe” lock.
Thus, there are four industry-standard solenoid-type electromechanical locks that must be stocked in inventory: the two different voltages (12 and 24 volts), for use with the two different standard voltages used in solenoid-type control systems, and the two different default states for the unpowered lock.
In the unpowered state, a “fail safe” solenoid lock is unlocked. When power is applied to the fail safe solenoid lock drive in the lock, a coil in the solenoid produces a magnetic field that moves a solenoid rod against the spring biasing pressure to lock the lock mechanism. To keep the lock continuously in the locked position, power must be continuously applied to the solenoid. When power is removed from the fail safe solenoid lock, the biasing spring returns the solenoid rod and the lock mechanism to the unlocked or “safe” position, allowing passage through the door.
Fail safe locks may be used, for example, in doors to public areas or building exits that are not normally used. In the event of a fire, the loss of power to the doors automatically unlocks such doors allowing safe passage therethrough during the emergency.
A “fail secure” solenoid lock has its solenoid rod biased in the opposite way. In the unpowered state it is in the locked state. When power is applied, the solenoid coil moves the solenoid rod against the spring biasing pressure to unlock the lock mechanism. With power removed, the biasing spring returns the lock mechanism to the locked or “secure” position.
Fail secure locks may be used, for example, in interior doors to high security rooms in the interior of the building. The locks on such interior doors are typically designed to allow egress from the locked room regardless of the locked or unlocked state of the lock mechanism on the door. The lock mechanism is designed to prevent unauthorized entry into the secured area from a hallway or public area, but does not prevent those within from exiting the secure area.
If power to the lock is interrupted for any reason the solenoid-type lock drive automatically returns to its default state and locks the door. Unless a key is used to manually operate the fail secure lock, it is not possible to enter the secured area even when power is intentionally cut to the lock mechanism.
One problem with the solenoid drive system for locks is that each of the four different types of locks (12 and 24 volt solenoids in fail safe and fail secure models) must be manufactured and held in inventory to meet the needs of customers. There is a need for a single lock mechanism drive capable of replacing each of the four different types of locks.
A related problem is that the four solenoid-type lock drives often require several components and/or internal connections within the lock mechanism. There is a need for a modularized lock drive to simplify manufacturing and reduce errors and assembly time.
Many solenoid-type lock drives include various sensors to detect the state of the door lock and the position of internal lock components. Sensors may be used to detect when the handle on each side of the door has been rotated, when the latchbolt is refracted or extended, etc. The installation and interconnection of these sensors during manufacturing is labor intensive and costly. There is a need for an improved interconnection and mounting of such sensors in combination with other improvements in the lock drive to integrate the installation.
Another problem with such prior art solenoid-type lock drives is the waste of power due to the need to keep the solenoid constantly powered. There are many applications where it is desirable to use a fail secure lock, but the lock must be held in the unlocked state for long periods, such as during an entire working day. There are also many applications where it is desirable to use a fail safe lock and the lock must remain locked during long periods.
By some estimates, up to forty percent of the time, solenoid locks are powered and the solenoid is held in the non-default state against the biasing force of the solenoid spring. There is a need for a lock drive that can reduce the energy cost of holding the lock in the non-default state, while still returning the lock to the default state when power is lost, as may happen in a power failure, during a fire or when power is intentionally cut in an attempt to access a secure area.
A related problem is that by constantly supplying power to a solenoid lock (to hold it in the non-default state), the lock is continuously dissipating power in the solenoid coil, which results in heating of the lock body. Although the lock and the solenoid coil can be designed for the heating produced in continuous duty operation, this heating is generally considered to be objectionable. The handle connected to such a lock may become objectionably warm and the heating may affect any nearby electronic components. There is a need for a lock mechanism that does not produce heat when held in the non-default state, but which can be operated with a 12 or 24 volt solenoid-type lock control system.
Solenoid-type lock drives have previously been used where power is continuously available. As such, low cost has been a primary motivating factor and energy conservation has not been properly considered. There is a need for a lock mechanism having a low power lock drive that will function as a direct drop-in replacement for a solenoid-type lock without requiring replacement of its associated solenoid-type lock control system and which will have the same feature of returning to a known default state when power is removed. In particular there is a need for a low power lock drive which can be used in combination with an existing installed base of solenoid locks.
Solenoid locks move from the default state when power is applied. As they move, they store energy in a biasing spring in the solenoid. As long as the lock is powered, it remains in the non-default state and energy remains stored in the biasing spring. As soon as power is removed, the stored energy in the biasing spring drives the lock mechanism to its locked or unlocked default state.
Any low power replacement for this type of industry standard solenoid lock drive system must have this same basic operation—it must move from a default state to a non-default state when power is applied and it must return to the default state when power is removed.
One type of known low power lock drive system uses a motor to drive a locking element between locked and unlocked states. Motors have the advantage that they can sit unpowered for long periods after driving the locking element to the desired state. However low power motorized designs do not operate against a biasing spring that returns the lock to a default state. If a default spring were to be used, power would have to be supplied to hold the motor against the return spring.
Motorized drive type locks must be operated by a motorized drive type of control system that actively moves the lock between the locked and unlocked states. Although motorized drive type locks may be mechanically very similar to the four solenoid-type locks, the motorized drive type control system is significantly different. The motorized drive type control system must always provide power to the lock. To ensure that the lock is in a desired state, the lock control system must typically monitor the position of the motor or associated locking element. This active driving and monitoring for a motorized drive contrasts with the simplicity of a spring biased solenoid-type lock drive.
Motorized drive type locks are typically used in more expensive applications, such as in low power battery operated lock applications which use an electronic key. The electronic key may be a key card of the type used in many hotels, a keypad mounted on or near the door, an RFID or similar secure proximity detection system, a biometric-type identification system that matches fingerprints, iris patterns, voice or faces, etc. Typically, the electronics for deciding when the lock should be opened are located in a control lock housing that is separate from the housing for the mechanical components of the lock mechanism with its motorized lock. The motor in the motorized drive is located in the mechanical lock housing and installed with the lock. All other control electronics are typically located in a control housing mounted separately outside the mechanical lock housing and connected thereto by a control cable accessible only from inside the secure area.
In the motorized lock drive, wires connect the motor within the body of the lock mechanism to the housing for the control electronics. A battery is located in the control system housing, not the lock housing and the motorized control system provides all control signals to the motor inside the lock housing whenever it is necessary to drive the motor in the lock from one position to the other.
Although motorized lock drives for use in sophisticated battery operated systems are known, there is a need for a motorized lock drive with integrated control electronics located within the lock housing for direct replacement of solenoid locks. Unlike known motorized drive type locks, a suitable solenoid replacement lock drive must have the lock drive electronics within the lock housing or directly associated with the lock to allow for direct replacement of a solenoid lock.
Moreover, the control electronics for the motor must emulate the functionality of a solenoid lock by returning to a known default state in the absence of power. This combination of a low power motor drive and motor control to replace a solenoid lock, where the motor and motor control emulate solenoid functionality and are not intended for battery operation, but are intended for use in a solenoid system having the higher power of non-battery powered systems has not heretofore been available.
Known motorized locks intended for use with battery operated designs make efficient use of the battery power because the lock drive motor uses no power unless it is changing state. However, it has been found that the mechanical efficiency of conventional motorized locks is also less than is desirable. This reduced mechanical efficiency results in an undesirable excess power loss each time the lock changes state due to the need to overcome excess friction.
More specifically, the motor axis of conventional motor drive systems is not axially aligned with the motion of the locking element or the axis of rotation of the lock hub. The motor of such conventional designs is offset from the line of motion of the locking element. To move the locking element, the motor must drive a lever, offset spring or other mechanical interconnect instead of driving the locking slide directly. The force produced by the motor in known motorized lock drives is offset from the desired direction of motion of the locking element.
This offset requires some type of interconnecting element between the lock drive motor and the locking element. It has not heretofore been recognized that this offset and the interconnecting element produce significant friction that must be overcome and decreased performance.
There is a need for a motorized lock drive with improved mechanical efficiency in both battery operated and solenoid replacement applications. More specifically, there is a need for a low power, motorized lock drive and/or a motorized lock drive that emulates a solenoid-type lock drive in which the motor is positioned in a direct line with motion of the locking element and/or the rotation of the lock hub to reduce mechanical inefficiency of the lock drive.
The prior art offset axis motorized lock drive system for battery operated applications represents a fifth type of lock mechanism that must be manufactured and held in inventory in addition to the four solenoid-type lock mechanisms. None are interchangeable with the other as each is designed for a different application or a different type of lock control system. All of the five types may have substantially the same type of mechanical lock components and hardware with only the electronic drive system being different, but all five types must be held in inventory. There is a need for a lock drive that can easily be switched between each of the four solenoid types, and preferably, also to the motor drive type in order to reduce inventory costs.
As described above, known motorized drive control systems must send specific signals whenever it is necessary to lock or unlock the mechanism. This operation has the advantage of reduced power usage because no power is used except when the lock drive is changing state. However, motorized lock drives do not rely upon the lock to return to a default state and cannot be used to replace a solenoid lock controlled by a solenoid-type lock control system.
The solenoid-type lock control system has only two states—power on and power off. Thus a solenoid-type lock control system is significantly different from a motorized drive lock control system and a lock mechanism with a motorized lock drive is not suitable for use with the control system for a lock mechanism having a solenoid-type lock drive. It would be desirable to be able to remove a solenoid lock that spends much of its time powered on and replace it with a drive having a motorized drive system that spends substantially all of its time in the unpowered state.
However, a lock mechanism having a motorized lock drive of the type described above cannot directly replace a solenoid-type lock due to the differences between the required control systems.